Current-controlling device



Get. 2, 1928.

W. R. BALLARD CURRENT CONTROLLING DEVICE Filed Dec. 2, 1924 INVENTOR WRBI [M409 BY ATTORNEY Patented Oct. 2 1928.

UNITED STATES 1,685,801 PATENT OFFICE.

WILLIAM B. BALLARD, or NEW ROCHELLE, NEW Yoax, assrenoa 'ro manrcm'rELnrxoNn AND 'rnLaemrr COMPANY, A CORPORATION orv NEW YORK.

CURRENT-CONTROLLING D TEVICE.

Application Med December 2, 1924, Serial No. 753,522, and in JapanOctober 6, 1924.

This invention relates to current controlling devices, and particularlyto a resistance element having no inductance, substantially no capacity,and which is nonmicrophonic.

In the design and construction of radio receiving apparatus, and otherty es of electrical apparatus, it is frequently esirable to with t eattac ed drawing of which Figure 1 shows a simple form'of embodiment ofthe invention; and Fig.2 shows some of the details em loyed in thearrangement shown in Fig. 1 il ustrating the method of construction.

In Fi 1 the members 1 and 2, of insulating materia, together with thebolts 3 and 4, serve to clamp tightly a plurality of sheets of highresistance material which. constitutes the resistance element of thedevice. These sheets are represented by 5 and 6 of Fig. 2. A simplemethod for producing these resistance elements consists in dipping asheet of cardboardor other suitable material in black India ink which,as is well known, consists principally of ground carbon, After beingcoated, prefera l on both sldes, the sheet should be thoroug 1y dried soas to avoid any substantial conductance through the material upon whichthe carbon has been deposited. Other material than the carbon-coatesheets may, of course, be employed for resistance material; as, forexample, thin sheets of pure carbon or equivalent material.

In building up the resistance unit, a sheet of high resistance materialsuch as 6 is placed upon one of the clamping members 1 and a fine, bareco per wire is wound back and forth across the face of the sheet in themanner shown in Fig. 2, the wire being held by pins, such as 7 and 8,which may be inserted either in each face of' the clamping block asshown, or u on a mounting block which may be employe in the assemblingof this apparatus. To produce a resistance unit having equal steps ofresistance, the distance between the successive crossings of the wireover the r wire was wound over the first sheet.

face of the sheet 6 should be substantially the same throu hout thelength of the sheet. A second coated first sheet, across which the wirehas been wound ,and then another length of bare cop,-v per wire is woundback and forth over the second sheet in the same way in which the Thenumber of sheets employed will, of course, depend upon the magnitude ofthe resistance desired. After the required number of sheets ofresistance material have been placed in position they should be boundtightly together between the clamping members 1 and 2 by means of thebolts 3 and 4'. The loops under the pins should then be cut and all ofthe wires extending across the adjacent sheets at the same relativeposition should be twisted together and fastened beneath aswitch-contact point as shown in Fig. 1. Thus, the wires extendingtransversely between the sheets at the position A, are bound togetherunder the contact point 9; those at position B are connected withcontact point 10, and similarly the other groupsof wires are connected.The portions of the wires which were looped around the pins on the sideof the clamping member opposite to that in which the contact points areplaced, may be cut oil close to the edges of the sheets through whichthey pass.

sheet is then placed over the I After completion, the unit shouldpreferably be sealed against moisture by coating with shellac or othersuitable material.

The last group of wires which is connected with the contact point 11 mayconstitute one terminal of a potentiometer, and the movable arm 12 ofthe switch the other terminal. resistance will therefore depend upon thesetting of the arm 12. Thus, when the. arm 12 rests upon the contactpoint 9 the magnitude of the resistance between the arm 12 and thecontact point 11 is the resultant of the re sistance of-all the sheetsin parallel between the position A, and position X. Other settings ofthe arm 12 will decrease the resistance between the contact point 11 andthe arm 12.

From the foregoing description, it will be a parent that the product isin effect, a block 0? carbon or similar high resistance material havinga plurality of substantially parallel conductors set therein, eachconductor extending transversely through the block. The important pointto be considered in carrying The out the invention is to rovide arelatively large surface of contact .etween the low resistance element,viz, the terminating conductors and the high resistance element, viz,the carbon or equivalent material in either block or laminated form.

This invention is not limited to the particulariorm of embodiment shownand described herein, but obviously may be made in other forms withoutdepartin from the spirit and scope of the appended rilaims.

What is claimed is: j

1. In a resistance device, the combination with a plurality of sheets ofresistance material of a plurality of separate, spaced conductors lyingtransversely between adjacent sheets, the conductors between any twosheets being substantially directly above and below the conductorsbetween the adjacent sheets, means to clamp together all of the saidsheets, and a plurality of terminals each of which serves to terminateall of the conductors similarly located between the adjacent sheets.

2. In a resistance device, the combination with a plurality of sheets ofresistance material, of a plurality of separate, spaced conductorsbetween the said sheets, the spacing being such that all similarlypositioned conductors will lie substantially in the same verticaltransverse plane, means to clamp the said sheets, and a plurality ofterminating means, each individual to and connected with all of thewires lying in the same vertical plane.

3. In a resistance device, the combination with two sheets coated withhigh resistance material, of a plurality of separate, spaced wires lyingtransversely between the said sheets and separating the said sheets intoa plurality of resistance units, and means for clamping the said sheets.

4. In a resistance device, the combination with a plurality of sheetscoated with high resistance material, of a plurality of wires lyingtransversely between adjacent sheets to separate each ofsaid sheets intoa plurality of resistance units, the wires between any two of saidsheets being in substantially the same vertical transverse plane as thesimilar wires between the other adjacent sheets, and means for clampingthe said sheets.

In testimony whereof, I have signed my name to this specification this1st day of December, 1924.

WILLIAM R. BALLARD.

